There have been many publications in recent years relating to 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0.sup.5,9.0. sup.3,11 ] dodecane, also known as hexanitrohexaazaisowurtzitane.
These publications describe the physical, chemical and detonating properties of this compound and/or various polymorphic forms, as well as its use in explosive compositions, propellants or powders for weapons.
Mention may be made, for example, of F. Foltz, who, in Propellants, Explosives, Pyrotechnics, 19, 63-69 (1994), studies the thermal stability of the epsilon polymorph in a poly(urethane-ester) and who, in Propellants, Explosives, Pyrotechnics, 19, 19-25 (1994), studies the thermal stability of the four polymorphic forms known as the alpha, beta, gamma and epsilon forms.
However, information relating to its synthesis is very rare, imprecise and insufficient for a person skilled in the art, even with his broad knowledge, to be able to prepare it.
While the writers of the abovementioned publications sometimes mention that the compound has been obtained from hexabenzylhexaazaisowurtzitane, they never describe how.
The most specific information relating to the synthesis appears in Patent Application PCT WO 97/20785, relating to the synthesis of tetraacetyldibenzylhexaazaisowurtzitane from hexabenzylhexaazaisowurtzitane.
It is mentioned therein that it is possible to obtain hexanitrohexaazaisowurtzitane from this intermediate acetylated compound by firstly reacting it with a nitrosating agent and then subsequently with a nitrating agent, but no example of such a reaction is disclosed and no details relating to the operating conditions (temperature, concentration of the acids, medium, and the like) are given.
Arnold T. Nielsen, at the Long Beach (Calif., U.S.A.) congress organized by the American Defense Preparedness Association and held at the Queen Mary Hotel on Oct. 27-29, 1986, also disclosed the synthesis of tetraacetyldibenzylhexaazaisowurtzitane by reaction of hexabenzylhexaazaisowurtzitane with acetic anhydride in the presence of hydrogen and of Pd/C as catalyst.
The writer also indicates that he had studied numerous operating conditions for the nitration of tetraacetyldibenzylhexaazaisowurtzitane with the aim of obtaining hexanitrohexaazaisowurtzitane but that this compound could never be obtained.
Despite this preconception and this imprecise information, operating conditions have now been found which make it possible to obtain hexanitrohexaazaisowurtzitane from tetraacetyldibenzylhexaazaisowurtzitane with an excellent yield. The hexanitrohexaazaisowurtzitane thus obtained exists in the alpha polymorphic form, with reference to the abovementioned publications by Foltz. Its density is 1.97 g/cm.sup.3.
Now, according to the same publications by Foltz, it is the epsilon polymorphic form which has the highest density (2.04 g/cm.sup.3) and which thus appears to be the most advantageous, in particular for the use thereof in pyrotechnic compositions.
While certain properties and characteristics of the epsilon form of hexanitrohexaazaisowurtzitane are known to a person skilled in the art, the information included within this actual state of the art, even complemented by the broad knowledge of a person skilled in the art, does not allow him to prepare it and to isolate it.
A person skilled in the art is thus in search of processes which make it possible to obtain this epsilon polymorphic form.